Manufacture of reflectors.



BEST AVAlLABLE coP UNITED STATES PATENT I OFFICE.

SHERARD OSBORN COlVPER-OOLES, OF LONDON, ENGLAND, ASSIGNOR OF ONE-HALF TO THE REFLECTOR SYNDICATE, LIMITED, OF SAME PLACE.

MANUFACTURE OF REFLECTORS.

SPECIFICATION forming part of Letters Patent No. 660,416, dated October 23, 1900.

Application filed November 7, 1898. Serial No. 695,782. (No specimens.)

T at whont it may concern:

Be it known that I, SHERARD OSBORN Cow- PER-COLES, engineer, a subject of the Queen of Great Britain, residing at Grosvenor Man sions, Victoria street, London, England, have invented new and useful Improvements in the Manufacture of Reflectors, of which the following is a specification.

This invention relates to improvements in the manufacture of parabolic reflectors by the electrodeposition of the same on suitable molds.

An important feature of the present invention consists in the employment of molds of speculum metal instead of the glass molds heretofore used, thus enabling a highly-polished, truly-shaped, and electrically-cond uctive surface to be obtained without the special treatment necessary where glass is used. A further important feature of the invention consists in the application of a reflecting and protecting, surface of platinum to the electrically-deposited reflector.

According to the said invention the speculum metal is cast in an iron mold heated almost to the melting-point of the said metal, which may advantageously consist of tin, fifteen parts, copper, thirty-two parts, and arsenic, one part; or tin, one part, and copper, two parts. This metal is poured carefullyinto the mold through a central feed-opening or runner, so as to insure a sound casting free from blowholes, the edge of the mold being left open. The casting is then removed from the mold and is brought in any convenient manner to the true geometrical shape required for the finished mold, after which it is provided with as high a polish as possible. It is then coated with a thin film of beeswax dissolved in a suitable solvent to facilitate the removal of the mirror from the mold. This film of wax is so thin that it does not act as an insulator to the mold and does not therefore require metallizing. The body of the reflector is then electrically deposited on the mold in one or more layers, the surface next the mold acquiring a highly-polished and true surface corresponding to that of the mold.

When the deposition has been carried on to the required extent, it is stopped and the reflector-backing and mold detached from one I another, which may be readily done by heat-- ing them slightly, (preferably by dipping them in hot water,) when the difference in expansibility will cause them to separate. That surface of the reflector which was adjacent to the mold is then cleanedchemically-for example, with a solution of potassium cyanid or hydrateand the reflecting and protecting surface of platinum, palladium, or chromium is applied to it by means of electrical deposition.

The bath used for the electrodepositiou of the platinum may be composed of freshlyprecipitated double chlorid of platinum and ammonium dissolved in a boiling concentrated solution of neutral citrate of sodium. The solution is preferably used in the cold state and should contain about one and one-half ounces of metal to the gallon; The current should have a density of about three am peres per square foot of cathode-surface, and the difference of potential between the terminals of the depositing-cell should be about 0.75 of a volt.

What I claim is 1. A process for manufacturing a reflector by electrodeposition, consisting in coating the surface of a metal mold with a film of wax which is so thin that it does not act as an insulator, electrolytically depositing the metal body of the reflector on said coated surface, separating the mold and body by varying the temperature, chemically cleaning the surface of the .body that was in contact with the mold, and then electrolytically depositing a reflecting and protecting surface on said cleansed surface, substantially as described.

2. A process for manufacturing a reflector by electrodeposition, consisting in coating the surface of a speculum-metal mold with a film of wax which is so thin that .it does not act as an insulator, electrolytically depositing the metal body of the reflector on said coated surface, separating the mold and body by immersing them in hot water, chemically cleaning the surface of the body that was in contact with the-mold, and then electrolytically depositing a reflecting and protecting surface on said cleansed surface, substanprocess for 5: aufacfliafh g a reflector oy electrodepositicu, consistihg in coating the surface of a speculum-metal mold with a film of wax which is so thin that it does not act as an insulator, electrolytically depositing the metal body of the reflector on said coated so 1'- face, separating the mold and body by immersing them in hot water, chemically cleansing the surface of the body that was in contact with the mold, and then electrolytically depositing a reflecting and protecting surface of platinum on said cleansed surface, substantially as described.

4. A process for man ufacturinga reflector by electrodeposition, consisting in coating the surface of a speculum-metal mold with a film of wax which is so thin that it does not w act as an insulator, electrolytically deposit- Witnesses:

ally depositing a reflecting and protecting surface'of platinumfrom asolution of freshlyprecipitated gouble chlorid of platinum and ammonium in: a concentrated solution of neutral citrate of sodium on said cleansed surface, substantially as described.

In testimony whereof I have hereunto set my hand, in presence of two subscribingwitnesses,this 71th day'of October,TT -I898.

SHERARD OSBORN GOWPER-COLES;

GEO. P. S KELSEY, WALTER E. RocHEl 

